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References: <20201127161451.17922-1-rbergant@redhat.com> <F08098E1-7E04-4ECA-852A-C93E837E4EBF@oracle.com>
In-Reply-To: <F08098E1-7E04-4ECA-852A-C93E837E4EBF@oracle.com>
From:   Roberto Bergantinos Corpas <rbergant@redhat.com>
Date:   Fri, 27 Nov 2020 18:14:04 +0100
Message-ID: <CACWnjLwx_Lj4HXr4ifaSzvjRvQTj-QuC7VeYYxNpLJwBh=uuXQ@mail.gmail.com>
Subject: Re: [PATCH] sunrpc: clean-up cache downcall
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Bruce Fields <bfields@fieldses.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Hi Bruce!

 Thanks for comments!, i'll send a v2 with mechanical errors fixed
based on v5.10-rc5.

rgds
roberto

On Fri, Nov 27, 2020 at 5:52 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
> Hi Roberto-
>
> I spotted some mechanical problems.
>
>
> > On Nov 27, 2020, at 11:14 AM, Roberto Bergantinos Corpas <rbergant@redhat.com> wrote:
> >
> > We can simplifly code around cache_downcall unifying memory
>
> ^simplifly^simplify
>
> > allocations using kvmalloc, this have the benefit of getting rid of
>
> ^, this have^. This has
>
> > cache_slow_downcall (and queue_io_mutex), and also matches userland
> > allocation size and limits
> >
> > Signed-off-by: Roberto Bergantinos Corpas <rbergant@redhat.com>
>
> Assuming Bruce is copacetic with this patch, the change looks
> appropriate for the v5.11 merge window. However, this patch
> doesn't appear to apply to v5.10-rc5. Might be because
> 27a1e8a0f79e ("sunrpc: raise kernel RPC channel buffer size")
> was already merged?
>
>
> > ---
> > net/sunrpc/cache.c | 41 +++++++++++------------------------------
> > 1 file changed, 11 insertions(+), 30 deletions(-)
> >
> > diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> > index baef5ee43dbb..1347ecae9c84 100644
> > --- a/net/sunrpc/cache.c
> > +++ b/net/sunrpc/cache.c
> > @@ -777,7 +777,6 @@ void cache_clean_deferred(void *owner)
> >  */
> >
> > static DEFINE_SPINLOCK(queue_lock);
> > -static DEFINE_MUTEX(queue_io_mutex);
> >
> > struct cache_queue {
> >       struct list_head        list;
> > @@ -905,44 +904,26 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
> >       return ret;
> > }
> >
> > -static ssize_t cache_slow_downcall(const char __user *buf,
> > -                                size_t count, struct cache_detail *cd)
> > -{
> > -     static char write_buf[8192]; /* protected by queue_io_mutex */
> > -     ssize_t ret = -EINVAL;
> > -
> > -     if (count >= sizeof(write_buf))
> > -             goto out;
> > -     mutex_lock(&queue_io_mutex);
> > -     ret = cache_do_downcall(write_buf, buf, count, cd);
> > -     mutex_unlock(&queue_io_mutex);
> > -out:
> > -     return ret;
> > -}
> > -
> > static ssize_t cache_downcall(struct address_space *mapping,
> >                             const char __user *buf,
> >                             size_t count, struct cache_detail *cd)
> > {
> > -     struct page *page;
> > -     char *kaddr;
> > +     char *write_buf;
> >       ssize_t ret = -ENOMEM;
> >
> > -     if (count >= PAGE_SIZE)
> > -             goto out_slow;
> > +     if (count >= 32768) { /* 32k is max userland buffer, lets check anyway */
> > +             ret = -EINVAL;
> > +             goto out;
> > +     }
> >
> > -     page = find_or_create_page(mapping, 0, GFP_KERNEL);
> > -     if (!page)
> > -             goto out_slow;
> > +     write_buf = kvmalloc(count + 1, GFP_KERNEL);
> > +     if (!write_buf)
> > +             goto out;
> >
> > -     kaddr = kmap(page);
> > -     ret = cache_do_downcall(kaddr, buf, count, cd);
> > -     kunmap(page);
> > -     unlock_page(page);
> > -     put_page(page);
> > +     ret = cache_do_downcall(write_buf, buf, count, cd);
> > +     kvfree(write_buf);
> > +out:
> >       return ret;
> > -out_slow:
> > -     return cache_slow_downcall(buf, count, cd);
> > }
> >
> > static ssize_t cache_write(struct file *filp, const char __user *buf,
> > --
> > 2.21.0
> >
>
> --
> Chuck Lever
>
>
>